The efficient use of energy is urgently needed from an economical and ecological perspective. Energy conservation is therefore a measure for both lowering costs and protecting the environment, and it can be achieved either by cutting energy use or through intelligent technical solutions. The energy-related and environmental performance of heating boilers has a great deal to do with this issue. Up to now, evaluations of energy efficiency were based mainly on static approaches. However, the interaction between the system and building is dynamic. As a result, the efficiency specified by heating boiler manufacturers deviates substantially in many cases from the degree of utilization achieved during operation in practice.
This is due, among other things, to the fact that systems of this type were frequently overdimensioned due to a false understanding of “the need for safety and comfort.” This applies not only to private systems, but to a large extent also to buildings used for public and commercial purposes. The consequence of this overdimensioning is that the thermal systems are operated in uneconomical partial load situations for most of the heating period. This unsatisfactory situation results in the need to determine the actual heat requirements of a building to be heated to improve the building's energy efficiency so that the heating system can be optimally adapted thereto.
Up to now, the energy efficiency for heating an existing building has usually been ascertained as follows: The building to be subjected to an energy evaluation is assigned to its year of origin according to a typology. Based on plans or an inspection, the area is surveyed to ascertain the building geometry. The corresponding heat transfer coefficients are ascertained through comparison with flat-rate figures from a component catalog. Using existing software programs, the transmission and ventilation heat losses are calculated on the basis of this data, and these losses are used to calculate the heat demand. System efficiency is calculated on the basis of a heating system catalog, the energy efficiency being concluded in the evaluation from the system technology used and the year of construction. Based on the data ascertained in this manner, an overall assessment with regard to final energy demand, primary energy demand, and CO2 emissions is drawn up, and the building is placed on a rating scale.
This method is controversial due to the somewhat subjective evaluation factors, resulting in the need for a method based on an objective foundation.
The more the installed power deviates from the connected load of the building (overdimensioning), the farther removed from the optimum the energy efficiency of a heating system becomes. The determination of the connected load of the building therefore performs a key function in improving energy efficiency. In the case of heating, the connected load of the building is the maximum heat loss of the building and is calculated for the lowest local statistical outside temperature according to regulation DIN 4701/VDI 2067.
Heating systems are configured, i.e., engineered, with respect to this connected heating load. The installed power (nominal power) is sufficient to equalize the building's transmission and ventilation losses with continuous prevalence of the design temperature, taking wind conditions into account. The power needed to provide hot water is added to this value. The specific user behavior is, in principle, not taken into account.
Methods for determining the connected load via metrology have occasionally been used which calculate this connected load by measuring heat flow, but without providing a statement on ways to optimize a system. In addition, patent applications have been filed for methods which, in part, integrate the boiler's fuel performance into the calculation. In the case of these methods, however, the unsteady behavior of a heating system caused by cycling or modulating the boiler is ignored or not adequately considered. This unsteady behavior occurs when the power requirement lies below the installed power, thus determining the gap between the actual degree of utilization and the efficiency defined by the manufacturer or measured at certain points by waste gas analysis equipment.
A method is known from DE 3 730 529 A1 for measuring a dimensional characteristic of a heating unit of a heating system defined by the ratio between the setpoint capacity utilization and the actual capacity utilization, in which the heat demand is determined by measuring the setpoint capacity utilization via measurement of the outside temperature at constant time intervals, forming an average value and multiplying it by a climate factor, as well as by simultaneously measuring the actual capacity utilization via continuous measurement of the switch-on period of the heating unit in relation to the preset minimum measuring time. The disadvantage of this method is that it requires a “measuring boiler,” which necessitates an extremely complex installation.
A method is known from DE 3 626 281 C2, in which the heat quantity is ascertained by a heat generator being used which has a high degree of efficiency. An observation period is divided into individual measuring periods, and the setpoint number of operating hours of the high-efficiency heat generator is related to the measuring period as a function of the outside temperature. The heat quantity transferred to the heated object within the observation period by the heat generator being used is then calculated from the nominal power thereof, taking into account the boiler efficiency and standby losses, as well as from the actual number of operating hours. The nominal power, in turn, is determined for a heat generator adjusted to the heat demand, using the quotient of the actual number of operating hours and setpoint number of operating hours. Although this method does not require such intensive intervention into the heating system as does the aforementioned DE 3 730 529 A1, numerous assumptions are nevertheless made which relate only to one average case, so that the ascertained heat demand may again deviate substantially from the actual heat demand. For example, only the boiler efficiency, which is ascertained once by the manufacturer, is used as a basis.
A method is known from DE 100 62 581, in which the outside temperature and a variable which is characteristic for an energy output of the heat source to the heating system are measured as a function of time, and the nominal heat demand is calculated from the measured values. However, the calculation of the energy output of the heat source is also based on different assumptions which distort an accurate determination of the actual energy output.
Accordingly, it may be desirable to specify a method and a system of the type mentioned above which does not have these disadvantages.